With the evolution of mobile communication, methods for increasing the data transfer rate have been studied. Technologies for increasing the data transfer rate may include a method of increasing the bandwidth of a signal, a method of increasing the transmit power, a method of increasing a signal-to-noise ratio at a receiver despite the use of the same transmit power, a method of simultaneously transmitting and receiving a plurality of data using a plurality of antennas, and the like.
As a specific example, the recently commercialized 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) communication system may increase the data transfer rate by transmitting and receiving signals in accordance with the Orthogonal Frequency Division Multiplexing (OFDM) scheme using a plurality of antennas. Technologies applied to increase the data transfer rate may include Multi-Input Multi-Output (MIMO) technology in which each of a transmitter and a receiver has a plurality of antennas, and simultaneously transmits modulation symbols via a plurality of antennas at the position of the same OFDM subcarrier, Single-User Multi-Input Multi-Output (SU-MIMO) technology in which a transmitter transmits signals to one receiver using a plurality of transmit antennas, and digital precoding technology in which, when one modulation symbol is transmitted to one receiver using a plurality of transmit antenna, an appropriate weight is multiplied by a modulation symbol transmitted via each transmit antenna. As another technology, there is Multi-User Multi-Input Multi-Output (MU-MIMO) technology in which when a transmitter simultaneously transmits modulation symbols to a plurality of receivers using a plurality of transmit antennas, a receiver receives only the desired symbols by applying a precoder value which is selected to maximize the magnitude of the signal that the receiver desires to receive, and to minimize the magnitude of interference signals.
Generally, in the LTE system having a plurality of antennas, in order for signals to be transmitted and received at any location in the cell, the beam width of each antenna of a transmitter may be set very wide in the horizontal direction. Therefore, the antenna gain used in the LTE system may be limited. In order to address these disadvantages, a scheme (hereinafter referred to as ‘analog beamforming technology’) has been introduced in which the entire beam width of an antenna is divided into narrow beam widths, and a plurality of beams corresponding thereto are formed. In addition, digital beamforming technology is also used in which when signals are simultaneously transmitted and received via a plurality of beams, the above-described digital precoding is additionally applied.
When the above-described analog beamforming technology is applied, a Base Station (BS) (also known as an evolved Node B (eNB)) and a Mobile Station (MS) (also known as a User Equipment (UE)) of the communication system may use a plurality of beams. In this case, there is a need for a process of selecting the optimal beam combination by performing channel estimation on combinations of beams for each of a plurality of antennas mounted on the BS and beams for each of a plurality of antennas mounted on the MS, for each of a DownLink (DL) and an UpLink (UL). Thus, when the typical analog beamforming is used, the time may be delayed and the resources may be wasted due to the process of selecting the optimal beam combination.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.